The embodiments described herein relate generally to power generation, and more specifically, to methods and systems for operating a power conversion system.
Solar energy has increasingly become an attractive source of energy and has been recognized as a clean, renewable alternative form of energy. Solar energy in the form of sunlight may be converted to electrical energy by solar cells. A more general term for devices that convert light to electrical energy is “photovoltaic cells.” Solar cells are a subset of photovoltaic (PV) cells.
In order to obtain a higher current and voltage, solar cells are electrically connected to form a solar module. In addition to a plurality of solar cells, the solar module may also include sensors, for example, an irradiance sensor, a temperature sensor, a voltage meter, a current meter, and/or a power meter. Solar modules may also be connected to form a module string. Typically, the direct current (DC) voltages output by the module strings are provided to a power converter, for example, a DC to alternating current (AC) voltage inverter. The DC to AC voltage inverter converts the DC voltage to three-phase AC voltage or current. The three-phase AC output from the DC to AC inverter is provided to a power transformer, which outputs a three-phase high-voltage AC power to an electrical grid.
In order to maximize the amount of time that an output power of a PV power generation system is at a desired level, it is common for the system to be designed with a PV array capable of producing more power than the power rating of the power converter. A “DC to AC ratio” is defined as the ratio of available power from the PV array divided by the rated output power of the power converter. For example, a particular system may have a DC to AC ratio of 1.25, where the ratio of available power from the PV array divided by the power converter rated output power is equal to 1.25. The rated output power of the power converter is typically selected to equal the power level desired to be provided to the electrical grid. A high DC to AC ratio is desirable because a system that includes a PV array having a higher available power than the converter rated output power maximizes the amount of time the output power level of the converter is at the desired level. However, a higher DC to AC ratio increases the chance of the power converter tripping or of converter damage.